Articles Having Improved Clarity, Prepared from Propylene-Ethylene Copolymers

ABSTRACT

Molded articles are prepared from propylene-ethylene copolymers and exhibiting improved clarity and strength properties. Articles prepared include bottles and other thin-walled articles. The articles are prepared using an isotactic propylene-ethylene random copolymer resin having an ethylene content of from about 0.5 to about 3 percent by total weight of copolymer, with a xylene solubles content of less than about 1.5 percent. The injection molded article may exhibit less than about 20 percent haze, as determined by ASTM D1003, at a thickness of about 0.08 inch (2.03 mm). Articles may also be prepared from similar copolymers having an ethylene content greater than about 3 percent by total weight of copolymer, with a xylene solubles content of less than about 4 percent by total weight of copolymer. These articles may exhibit less than about 13 percent haze, as determined by ASTM D1003, at a thickness of about 0.08 inch (2.03 mm).

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates generally to propylene polymers, and in particularto articles prepared from propylene-ethylene copolymers.

2. Background of the Art

Propylene-based polymers are popularly used in a number of thermoplasticprocessing operations. These operations include, for example, injectionmolding to produce relatively thin-walled products. These polymers haveconventionally been prepared via Ziegler-Natta catalysis, and the resulthas been found to be suitable for a wide variety of applications.However, some applications have indicated a need for improvedproperties, such as higher impact strength, lower melt temperatures, andhigher clarity than has been conventionally attained in polypropylene.In order to obtain these properties those skilled in the art havelearned that incorporation of a proportion of ethylene, to formpropylene-ethylene random copolymers, offers some of these advantages,as well as, in some cases, greater flexibility and increased toughness.

Despite these improvements, however, there is still a need in the artfor propylene-based polymers that exhibit, in particular, still greaterimprovements in clarity. This is because a number of the applicationsfor which the propylene-ethylene random copolymers are particularlywell-suited are also applications where transparency or a relativelyhigh degree of translucency is desirable. These applications include,for example, bottles, which require high clarity as well as hightoughness. One approach to obtaining such improvement in clarity hasinvolved the use of so-called clarity-enhancing agents. These agents maybe added to the molten polymer during pelletization, for example, orjust prior to injection of the polymer into the mold. Theclarity-enhancing agents generally operate by providing sites within thepolymer for crystallization, which enables formation of smallercrystallites. Since crystallites result in diffraction or reflection oflight, ensuring smaller crystallites reduces such occurrence, with theresult that clarity is increased. Unfortunately, use ofclarity-enhancing agents may increase the cost of preparing and usingthe polymers, and increasing their levels beyond a certain point may notbe feasible or desirable because of potential detriment to otherproperties of the polymer.

Thus, what is desired in the art are articles prepared frompropylene-ethylene random copolymers that exhibit improved clarity, withor without use of clarifying agents, and which also exhibit desirablelevels of other physical properties such as toughness, flexibility,impact strength, and the like.

SUMMARY OF THE INVENTION

In one embodiment the invention is an article comprising an isotacticpropylene-ethylene random copolymer having an ethylene content of fromabout 0.5 to about 3 percent by total weight of copolymer. Thispropylene-ethylene random copolymer may have a xylene solubles contentof less than about 1.5 percent by total weight of copolymer, and issuitable to form an injection molded article exhibiting less than about20 percent haze, as determined by ASTM D1003, at a thickness of about0.08 inch (2.03 mm).

In another embodiment the invention is an article prepared from anisotactic propylene-ethylene random copolymer having an ethylene contentof greater than about 3 percent by total weight of copolymer and axylene solubles content of less than about 4 percent by total weight ofcopolymer. This polymer is capable of forming an injection moldedarticle exhibiting less than about 13 percent haze, as determined byASTM D1003, at a thickness of about 0.08 inch (2.03 mm).

The articles may be prepared by a variety of methods, including but notlimited to injection molding.

DETAILED DESCRIPTION OF THE INVENTION

In one embodiment it has been found that articles exhibiting improvedclarity may be prepared from certain propylene-ethylene copolymers thatalso offer maintenance or improvement in physical properties such asmelt flow rate. When these copolymers are used in various applications,including preparation of injection molded articles, these copolymersimpart improved quality, particularly to commercially desirablethin-walled structures such as bottles and the like.

In one embodiment the propylene-ethylene copolymers are prepared using acatalyst selected from certain metallocene catalysts. Metallocenecatalysts may be characterized generally as coordination compoundsincorporating one or more cyclopentadienyl (Cp) groups (which may besubstituted or unsubstituted, each substitution being the same ordifferent) coordinated with a transition metal through n bonding

The Cp substituent groups may be linear, branched or cyclic hydrocarbylradicals. The cyclic hydrocarbyl radicals may further form othercontiguous ring structures, including, for example indenyl, azulenyl andfluorenyl groups. These additional ring structures may also besubstituted or unsubstituted by hydrocarbyl radicals, such as C₁ to C₂₀hydrocarbyl radicals.

A specific example of a metallocene catalyst is a bulky ligandmetallocene compound generally represented by the formula:

[L]_(m)M[A]_(n)

where L is a bulky ligand, A is a leaving group, M is a transition metaland m and n are such that the total ligand valency corresponds to thetransition metal valency. For example m may be from 1 to 3 and n may befrom 1 to 3.

The metal atom “M” of the metallocene catalyst compound, as describedthroughout the specification and claims, may be selected from Groups 3through 12 atoms and lanthanide Group atoms in one embodiment; andselected from Groups 3 through 10 atoms in a more particular embodiment,and selected from Sc, Ti, Zr, Hf, V, Nb, Ta, Mn, Re, Fe, Ru, Os, Co, Rh,Ir, and Ni in yet a more particular embodiment; and selected from Groups4, 5 and 6 atoms in yet a more particular embodiment, and Ti, Zr, Hfatoms in yet a more particular embodiment, and Zr in yet a moreparticular embodiment. The oxidation state of the metal atom “M” mayrange from 0 to +7 in one embodiment; and in a more particularembodiment, is +1, +2, +3, +4 or +5; and in yet a more particularembodiment is +2, +3 or +4. The groups bound the metal atom “M” are suchthat the compounds described below in the formulas and structures areelectrically neutral, unless otherwise indicated.

The bulky ligand generally includes a cyclopentadienyl group (Cp) or aderivative thereof. The Cp ligand(s) form at least one chemical bondwith the metal atom M to form the “metallocene catalyst compound”. TheCp ligands are distinct from the leaving groups bound to the catalystcompound in that they are not highly susceptible tosubstitution/abstraction reactions.

Cp typically includes 7-bonded and/or fused ring(s) or ring systems. Thering(s) or ring system(s) typically include atoms selected from group 13to 16 atoms, for example, carbon, nitrogen, oxygen, silicon, sulfur,phosphorous, germanium, boron, aluminum and combinations thereof,wherein carbon makes up at least 50% of the ring members. Non-limitingexamples include cyclopentadienyl, cyclopentaphenanthreneyl, indenyl,benzindenyl, fluorenyl, tetrahydroindenyl, octahydrofluorenyl,cyclooctatetraenyl, cyclopentacyclododecene, phenanthrindenyl,3,4-benzofluorenyl, 9-phenylfluorenyl, 8-H-cyclopent[a]acenaphthylenyl,7-H-dibenzofluorenyl, indeno[1,2-9]anthrene, thiophenoindenyl,thiophenofluorenyl, hydrogenated versions thereof (e.g.,4,5,6,7-tetrahydroindenyl, or “H₄Ind”), substituted versions thereof,and heterocyclic versions thereof.

Cp substituent groups may include hydrogen radicals, alkyls, alkenyls,alkynyls, cycloalkyls, aryls, acyls, aroyls, alkoxys, aryloxys,alkylthiols, dialkylamines, alkylamidos, alkoxycarbonyls,aryloxycarbonyls, carbomoyls, alkyl- and dialkyl-carbamoyls, acyloxys,acylaminos, aroylaminos, and combinations thereof. More particularnon-limiting examples of alkyl substituents include methyl, ethyl,propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl, phenyl,methylphenyl, and tert-butylphenyl groups and the like, including alltheir isomers, for example tertiary-butyl, isopropyl, and the like.Other possible radicals include substituted alkyls and aryls such as,for example, fluoromethyl, fluroethyl, difluroethyl, iodopropyl,bromohexyl, chlorobenzyl and hydrocarbyl substituted organometalloidradicals including trimethylsilyl, trimethylgermyl, methyldiethylsilyland the like; and halocarbyl-substituted organometalloid radicalsincluding tris(trifluoromethyl)silyl, methyl bis(difluoromethyl)silyl,bromomethyldimethylgermyl and the like; and disubstituted boron radicalsincluding dimethylboron for example; and disubstituted Group 15 radicalsincluding dimethylamine, dimethylphosphine, diphenylamine,methylphenylphosphine, Group 16 radicals including methoxy, ethoxy,propoxy, phenoxy, methylsulfide and ethylsulfide. Other substituents Rinclude olefins such as but not limited to olefinically unsaturatedsubstituents including vinyl-terminated ligands, for example 3-butenyl,2-propenyl, 5-hexenyl and the like. In one embodiment, at least two Rgroups, two adjacent R groups in one embodiment, are joined to form aring structure having from 3 to 30 atoms selected from the groupconsisting of carbon, nitrogen, oxygen, phosphorous, silicon, germanium,aluminum, boron and combinations thereof. Also, a substituent group Rgroup such as 1-butanyl may form a bonding association to the element M.

Each anionic leaving group is independently selected and may include anyleaving group, such as halogen ions, hydrides, C₁ to C₁₂ alkyls, C₂ toC₁₂ alkenyls, C₆ to C₁₂ aryls, C₇ to C₂₀ alkylaryls, C₁ to C₁₂ alkoxys,C₆ to C₁₆ aryloxys, C₇ to C₁₈ alkylaryloxys, C₁ to C₁₂ fluoroalkyls, C₆to C₁₂ fluoroaryls, and C₁ to C₁₂ heteroatom-containing hydrocarbons andsubstituted derivatives thereof; hydride, halogen ions, C₁ to C₆alkylcarboxylates, C₁ to C₆ fluorinated alkylcarboxylates, C₆ to C₁₂arylcarboxylates, C₇ to C₁₈ alkylarylcarboxylates, C₁ to C₆fluoroalkyls, C₂ to C₆ fluoroalkenyls, and C₇ to C₁₈ fluoroalkylaryls inyet a more particular embodiment; hydride, chloride, fluoride, methyl,phenyl, phenoxy, benzoxy, tosyl, fluoromethyls and fluorophenyls in yeta more particular embodiment; C₁ to C₁₂ alkyls, C₂ to C₁₂ alkenyls, C₆to C₁₂ aryls, C₇ to C₂₀ alkylaryls, substituted C₁ to C₁₂ alkyls,substituted C₆ to C₁₂ aryls, substituted C₇ to C₂₀ alkylaryls and C₁ toC₁₂ heteroatom-containing alkyls, C₁ to C₁₂ heteroatom-containing arylsand C₁ to C₁₂ heteroatom-containing alkylaryls in yet a more particularembodiment; chloride, fluoride, C₁ to C₆ alkyls, C₂ to C₆ alkenyls, C₇to C₁₈ alkylaryls, halogenated C₁ to C₆ alkyls, halogenated C₂ to C₆alkenyls, and halogenated C₇ to C₁₈ alkylaryls in yet a more particularembodiment; fluoride, methyl, ethyl, propyl, phenyl, methylphenyl,dimethylphenyl, trimethylphenyl, fluoromethyls (mono-, di- andtrifluoromethyls) and fluorophenyls (mono-, di-, tri-, tetra- andpentafluorophenyls) in yet a more particular embodiment; and fluoride inyet a more particular embodiment.

Other non-limiting examples of leaving groups include amines,phosphines, ethers, carboxylates, dienes, hydrocarbon radicals havingfrom 1 to carbon atoms, fluorinated hydrocarbon radicals (e.g., —C₆F₅(pentafluorophenyl)), fluorinated alkylcarboxylates (e.g., CF₃C(O)O⁻),hydrides and halogen ions and combinations thereof. Other examples ofleaving groups include alkyl groups such as cyclobutyl, cyclohexyl,methyl, heptyl, tolyl, trifluoromethyl, tetramethylene, pentamethylene,methylidene, methyoxy, ethyoxy, propoxy, phenoxy, bis(N-methylanilide),dimethylamide, dimethylphosphide radicals and the like. In oneembodiment, two or more leaving groups form a part of a fused ring orring system.

L and A may be bridged to one another. A bridged metallocene, forexample may, be described by the general formula:

XCp^(A)Cp^(B)MA_(n)

wherein X is a structural bridge, Cp^(A) and Cp^(B) each denote acyclopentadienyl group, each being the same or different and which maybe either substituted or unsubstituted, M is a transition metal and A isan alkyl, hydrocarbyl or halogen group and n is an integer between 0 and4, and either 1 or 2 in a particular embodiment.

Non-limiting examples of bridging groups (X) include divalenthydrocarbon groups containing at least one Group 13 to 16 atom, such asbut not limited to at least one of a carbon, oxygen, nitrogen, silicon,aluminum, boron, germanium and tin atom and combinations thereof;wherein the heteroatom may also be C₁ to C₁₂ alkyl or aryl substitutedto satisfy neutral valency. The bridging group may also containsubstituent groups as defined above including halogen radicals and iron.More particular non-limiting examples of bridging group are representedby C₁ to C₆ alkylenes, substituted C₁ to C₆ alkylenes, oxygen, sulfur,R₂C═, R₂Si═, —Si(R)₂Si(R₂)—, R₂Ge═, RP═ (wherein “═” represents twochemical bonds), where R is independently selected from the grouphydride, hydrocarbyl, substituted hydrocarbyl, halocarbyl, substitutedhalocarbyl, hydrocarbyl-substituted organometalloid,halocarbyl-substituted organometalloid, disubstituted boron,disubstituted Group 15 atoms, substituted Group 16 atoms, and halogenradical; and wherein two or more Rs may be joined to form a ring or ringsystem. In one embodiment, the bridged metallocene catalyst componenthas two or more bridging groups (X).

Other non-limiting examples of bridging groups include methylene,ethylene, ethylidene, propylidene, isopropylidene, diphenylmethylene,1,2-dimethylethylene, 1,2-diphenylethylene, 1,1,2,2-tetramethylethylene,dimethylsilyl, diethylsilyl, methyl-ethylsilyl,trifluoromethylbutylsilyl, bis(trifluoromethyl)silyl, di(n-butyl)silyl,di(n-propyl)silyl, di(i-propyl)silyl, di(n-hexyl)silyl,dicyclohexylsilyl, diphenylsilyl, cyclohexylphenylsilyl,t-butylcyclohexylsilyl, di(t-butylphenyl)silyl, di(p-tolyl)silyl and thecorresponding moieties, wherein the Si atom is replaced by a Ge or a Catom; dimethylsilyl, diethylsilyl, dimethylgermyl and/or diethylgermyl.

In another embodiment, the bridging group may also be cyclic, andinclude 4 to 10 ring members or 5 to 7 ring members in a more particularembodiment. The ring members may be selected from the elements mentionedabove, and/or from one or more of B, C, Si, Ge, N and O in a particularembodiment. Non-limiting examples of ring structures which may bepresent as or part of the bridging moiety are cyclobutylidene,cyclopentylidene, cyclohexylidene, cycloheptylidene, cyclooctylidene andthe corresponding rings where one or two carbon atoms are replaced by atleast one of Si, Ge, N and O, in particular, Si and Ge. The bondingarrangement between the ring and the Cp groups may be cis-, trans-, or acombination thereof.

The cyclic bridging groups may be saturated or unsaturated and/or carryone or more substituents and/or be fused to one or more other ringstructures. If present, the one or more substituents are selected fromthe group hydrocarbyl (e.g., alkyl such as methyl) and halogen (e.g., F,Cl) in one embodiment. The one or more Cp groups which the above cyclicbridging moieties may optionally be fused to may be saturated orunsaturated and are selected from the group of those having 4 to 10 ringmembers, more particularly 5, 6 or 7 ring members (selected from thegroup of C, N, O and S in a particular embodiment) such as, for example,cyclopentyl, cyclohexyl and phenyl. Moreover, these ring structures maythemselves be fused such as, for example, in the case of a naphthylgroup. Moreover, these (optionally fused) ring structures may carry oneor more substituents. Illustrative, non-limiting examples of thesesubstituents are hydrocarbyl (particularly alkyl) groups and halogenatoms.

In one embodiment, the metallocene catalyst includes CpFlu Typecatalysts (e.g., a metallocene incorporating a substituted Cp fluorenylligand structure) represented by the following formula:

X(CpR¹ _(n)R² _(m))(FlR³ _(p))

wherein Cp is a cyclopentadienyl group, Fl is a fluorenyl group, X is astructural bridge between Cp and Fl, R¹ is a substituent on the Cp, n is1 or 2, R² is a substituent on the Cp at a position which is proximal tothe bridge, m is 1 or 2, each R³ is the same or different and is ahydrocarbyl group having from 1 to 20 carbon atoms with R³ beingsubstituted on a nonproximal position on the fluorenyl group and atleast one other R³ being substituted at an opposed nonproximal positionon the fluorenyl group and p is 2 or 4.

In yet another aspect, the metallocene catalyst includes bridgedmono-ligand metallocene compounds (e.g., mono cyclopentadienyl catalystcomponents). In this embodiment, the at least one metallocene catalystcomponent is a bridged “half-sandwich” metallocene catalyst. In yetanother aspect of the invention, the at least one metallocene catalystcomponent is an unbridged “half sandwich” metallocene.

Described another way, the “half sandwich” metallocenes above aredescribed in U.S. Pat. No. 6,069,213, U.S. Pat. No. 5,026,798, U.S. Pat.No. 5,703,187, and U.S. Pat. No. 5,747,406, including a dimer oroligomeric structure, such as disclosed in, for example, U.S. Pat. No.5,026,798 and U.S. Pat. No. 6,069,213, which are incorporated byreference herein.

Non-limiting examples of metallocene catalyst components consistent with

-   the description herein include:-   cyclopentadienylzirconiumA_(n),-   indenylzirconiumA_(n),-   (1-methylindenyl)zirconiumA_(n),-   (2-methylindenyl)zirconiumA_(n),-   (1-propylindenyl)zirconiumA_(n),-   (2-propylindenyl)zirconiumA_(n),-   (1-butylindenyl)zirconiumA_(n),-   (2-butylindenyl)zirconiumA_(n),-   methylcyclopentadienylzirconiumA_(n),-   tetrahydroindenylzirconiumA_(n),-   pentamethylcyclopentadienylzirconiumA_(n),-   cyclopentadienylzirconiumA_(n),-   pentamethylcyclopentadienyltitaniumA_(n),-   tetramethylcyclopentyltitaniumA_(n),-   (1,2,4-trimethylcyclopentadienyl)zirconiumA_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(cyclopentadienyl)zirconiumA_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(1,2,3-trimethylcyclopentadienyl)zirconiumA_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(1,2-dimethylcyclopentadienyl)zirconiumA_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(2-methylcyclopentadienyl)zirconiumA_(n),-   dimethylsilylcyclopentadienylindenylzirconiumA_(n),-   dimethylsilyl(2-methylindenyl)(fluorenyl)zirconiumA_(n),-   diphenylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(3-propylcyclopentadienyl)zirconiumA_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(3-t-butylcyclopentadienyl)zirconiumA_(n),-   dimethylgermyl(1,2-dimethylcyclopentadienyl)(3-isopropylcyclopentadienyl)zirconiumA_(n),-   dimethylsilyl(1,2,3,4-tetramethylcyclopentadienyl)(3-methylcyclopentadienyl)zirconiumA_(n),-   diphenylmethylidene(cyclopentadienyl)(9-fluorenyl)zirconiumA_(n),-   diphenylmethylidenecyclopentadienylindenylzirconiumA_(n),-   isopropylidenebiscyclopentadienylzirconiumA_(n),-   isopropylidene(cyclopentadienyl)(9-fluorenyl)zirconiumA_(n),-   isopropylidene(3-methylcyclopentadienyl)(9-fluorenyl)zirconiumA_(n),-   ethylenebis(9-fluorenyl)zirconiumA_(n),-   mesoethylenebis(1-indenyl)zirconiumA_(n),-   ethylenebis(1-indenyl)zirconiumA_(n),-   ethylenebis(2-methyl-1-indenyl)zirconiumA_(n),-   ethylenebis(2-methyl-4,5,6,7-tetrahydro-1-indenyl)zirconiumA_(n),-   ethylenebis(2-propyl-4,5,6,7-tetrahydro-1-indenyl)zirconiumA_(n),-   ethylenebis(2-isopropyl-4,5,6,7-tetrahydro-1-indenyl)zirconiumA_(n),-   ethylenebis(2-butyl-4,5,6,7-tetrahydro-1-indenyl)zirconiumA_(n),-   ethylenebis(2-isobutyl-4,5,6,7-tetrahydro-1-indenyl)zirconiumA_(n),-   dimethylsilyl(4,5,6,7-tetrahydro-1-indenyl)zirconiumA_(n),-   diphenyl(4,5,6,7-tetrahydro-1-indenyl)zirconiumA_(n),-   ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconiumA_(n),-   dimethylsilylbis(cyclopentadienyl)zirconiumA_(n),-   dimethylsilylbis(9-fluorenyl)zirconiumA_(n),-   dimethylsilylbis(1-indenyl)zirconiumA_(n),-   dimethylsilylbis(2-methylindenyl)zirconiumA_(n),-   dimethylsilylbis(2-propylindenyl)zirconiumA_(n),-   dimethylsilylbis(2-butylindenyl)zirconiumA_(n),-   diphenylsilylbis(2-methylindenyl)zirconiumA_(n),-   diphenylsilylbis(2-propylindenyl)zirconiumA_(n),-   diphenylsilylbis(2-butylindenyl)zirconiumA_(n),-   dimethylgermylbis(2-methylindenyl)zirconiumA_(n),-   dimethylsilylbistetrahydroindenylzirconiumA_(n),-   dimethylsilylbistetramethylcyclopentadienylzirconiumA_(n),-   dimethylsilyl(cyclopentadienyl)(9-fluorenyl)zirconiumA_(n),-   diphenylsilyl(cyclopentadienyl)(9-fluorenyl)zirconiumA_(n),-   diphenylsilylbisindenylzirconiumA_(n),-   cyclotrimethylenesilyltetramethylcyclopentadienylcyclopentadienylzirconiumA_(n),-   cyclotetramethylenesilyltetramethylcyclopentadienylcyclopentadienylzirconiumA_(n),-   cyclotrimethylenesilyl(tetramethylcyclopentadienyl)(2-methylindenyl)zirconiumA_(n),-   cyclotrimethylenesilyl(tetramethylcyclopentadienyl)(3-methylcyclopentadienyl)zirconiumA_(n),-   cyclotrimethylenesilylbis(2-methylindenyl)zirconiumA_(n),-   cyclotrimethylenesilyl(tetramethylcyclopentadienyl)(2,3,5-trimethylclopentadienyl)zirconiumA_(n),-   cyclotrimethylenesilylbis(tetramethylcyclopentadienyl)zirconiumA_(n),-   dimethylsilyl(tetramethylcyclopentadieneyl)(N-tertbutylamido)titaniumA_(n),-   biscyclopentadienylchromiumA_(n),-   biscyclopentadienylzirconiumA_(n),-   bis(n-butylcyclopentadienyl)zirconiumA_(n),-   bis(n-dodecycicyclopentadienyl)zirconiumA_(n),-   bisethylcyclopentadienylzirconiumA_(n),-   bisisobutylcyclopentadienylzirconiumA_(n),-   bisisopropylcyclopentadienylzirconiumA_(n),-   bismethylcyclopentadienylzirconiumA_(n),-   bisnoxtylcyclopentadienylzirconiumA_(n),-   bis(n-pentylcyclopentadienyl)zirconiumA_(n),-   bis(n-propylcyclopentadienyl)zirconiumA_(n),-   bistrimethylsilylcyclopentadienylzirconiumA_(n),-   bis(1,3-bis(trimethylsilyl)cyclopentadienyl)zirconiumA_(n),-   bis(1-ethyl-2-methylcyclopentadienyl)zirconiumA_(n),-   bis(1-ethyl-3-methylcyclopentadienyl)zirconiumA_(n),-   bispentamethylcyclopentadienylzirconiumA_(n),-   bispentamethylcyclopentadienylzirconiumA_(n),-   bis(1-propyl-3-methylcyclopentadienyl)zirconiumA_(n),-   bis(1-n-butyl-3-methylcyclopentadienyl)zirconiumA_(n),-   bis(1-isobutyl-3-methylcyclopentadienyl)zirconiumA_(n),-   bis(1-propyl-3-butylcyclopentadienyl)zirconiumA_(n),-   bis(1,3-n-butylcyclopentadienyl)zirconiumA_(n),-   bis(4,7-dimethylindenyl)zirconiumA_(n),-   bisindenylzirconiumA_(n),-   bis(2-methylindenyl)zirconiumA_(n),-   cyclopentadienylindenylzirconiumA_(n),-   bis(n-propylcyclopentadienyl)hafniumA_(n),-   bis(n-butylcyclopentadienyl)hafniumA_(n),-   bis(n-pentylcyclopentadienyl)hafniumA_(n),-   (n-propylcyclopentadienyl)(n-butylcyclopentadienyl)hafniumA_(n),-   bis[(2-trimethylsilylethyl)cyclopentadienyl]hafniumA_(n),-   bis(trimethylsilylcyclopentadienyl)hafniumA_(n),-   bis(2-n-propylindenyl)hafniumA_(n),-   bis(2-n-butylindenyl)hafniumA_(n),-   dimethylsilylbis(n-propylcyclopentadienyl)hafniumA_(n),-   dimethylsilylbis(n-butylcyclopentadienyl)hafniumA_(n),-   bis(9-n-propylfluorenyl)hafniumA_(n),-   bis(9-n-butylfluorenyl)hafniumA_(n),-   (9-n-propylfluorenyl)(2-n-propylindenyl)hafniumA_(n),-   bis(1-n-propyl-2-methylcyclopentadienyl)hafniumA_(n),-   (n-propylcyclopentadienyl)(1-n-propyl-3-n-butylcyclopentadienyl)hafniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcyclopropylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcyclobutylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcyclopentylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcyclohexylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcycloheptylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcyclooctylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcyclononylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcyclodecylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcycloundecylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienylcyclododecylamidotitaniumA_(n),-   dimethylsilyltetramethylcyclopentadienyl(sec-butylamido)titaniumA_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(n-octylamido)titaniumA_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(n-decylamido)titaniumA_(n),-   dimethylsilyl(tetramethylcyclopentadienyl)(n-octadecylamido)titaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcyclopropylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcyclobutylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcyclopentylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcyclohexylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcycloheptylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcyclooctylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcyclononylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcyclodecylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcycloundecylamidotitaniumA_(n),-   methylphenylsilyltetramethylcyclopentadienylcyclododecylamidotitaniumA_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(sec-butylamido)titaniumA_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(n-octylamido)titaniumA_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(n-decylamido)titaniumA_(n),-   methylphenylsilyl(tetramethylcyclopentadienyl)(n-octadecylamido)titaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcyclopropylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcyclobutylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcyclopentylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcyclohexylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcycloheptylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcyclooctylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcyclononylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcyclodecylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcycloundecylamidotitaniumA_(n),-   diphenylsilyltetramethylcyclopentadienylcyclododecylamidotitaniumA_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(sec-butylamido)titaniumA_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(n-octylamido)titaniumA_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(n-decylamido)titaniumA_(n),-   diphenylsilyl(tetramethylcyclopentadienyl)(n-octadecylamido)titaniumA_(n),    and derivatives thereof.

As used herein, the term “metallocene activator” is defined to be anycompound or combination of compounds, supported or unsupported, whichmay activate a single-site catalyst compound (e.g., metallocenes, Group15 containing catalysts, etc.) Typically, this involves the abstractionof at least one leaving group (A group in the formulas/structures above,for example) from the metal center of the catalyst component. Thecatalyst components of the present invention are thus activated towardsolefin polymerization using such activators. Embodiments of suchactivators include Lewis acids such as cyclic or oligomericpolyhydrocarbylaluminum oxides and so called non-coordinating ionicactivators (“NCA”), alternately, “ionizing activators” or“stoichiometric activators”, or any other compound that may convert aneutral metallocene catalyst component to a metallocene cation that isactive with respect to olefin polymerization.

More particularly, it is within the scope of this invention to use Lewisacids such as alumoxane (e.g., “MAO”), modified alumoxane (e.g.,“TIBAO”), and alkylaluminum compounds as activators, to activatedesirable metallocenes described herein. MAO and other aluminum-basedactivators are well known in the art. Non-limiting examples of aluminumalkyl compounds which may be utilized as activators for the catalystsdescribed herein include trimethylaluminum, triethylaluminum,triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum and thelike.

Ionizing activators are well known in the art and are described by, forexample, Eugene You-Xian Chen & Tobin J. Marks, Cocatalysts forMetal-Catalyzed Olefin Polymerization: Activators, Activation Processes,and Structure-Activity Relationships 100(4) CHEMICAL REVIEWS 1391-1434(2000). Examples of neutral ionizing activators include Group 13tri-substituted compounds, in particular, tri-substituted boron,tellurium, aluminum, gallium and indium compounds, and mixtures thereof(e.g., tri(n-butyl)ammonium tetrakis(pentafluorophenyl)boron and/ortrisperfluorophenyl boron metalloid precursors). The three substituentgroups are each independently selected from alkyls, alkenyls, halogen,substituted alkyls, aryls, arylhalides, alkoxy and halides. In oneembodiment, the three groups are independently selected from the groupof halogen, mono or multicyclic (including halosubstituted) aryls,alkyls, and alkenyl compounds and mixtures thereof. In anotherembodiment, the three groups are selected from the group alkenyl groupshaving 1 to 20 carbon atoms, alkyl groups having 1 to 20 carbon atoms,alkoxy groups having 1 to 20 carbon atoms and aryl groups having 3 to 20carbon atoms (including substituted aryls), and combinations thereof. Inyet another embodiment, the three groups are selected from the groupalkyls having 1 to 4 carbon groups, phenyl, naphthyl and mixturesthereof. In yet another embodiment, the three groups are selected fromthe group highly halogenated alkyls having 1 to 4 carbon groups, highlyhalogenated phenyls, and highly halogenated naphthyls and mixturesthereof. By “highly halogenated”, it is meant that at least 50% of thehydrogens are replaced by a halogen group selected from fluorine,chlorine and bromine. In yet another embodiment, the neutralstoichiometric activator is a tri-substituted Group 13 compoundcomprising highly fluorided aryl groups, the groups being highlyfluorided phenyl and highly fluorided naphthyl groups.

Illustrative, not limiting examples of ionic ionizing activators includetrialkyl-substituted ammonium salts such as:

-   triethylammoniumtetraphenylboron,-   tripropylammoniumtetraphenylboron,-   tri(n-butyl)ammoniumtetraphenylboron,-   trimethylammoniumtetra(p-tolyl)boron,-   trimethylammoniumtetra(o-tolyl)boron,-   tributylammoniumtetra(pentafluorophenyl)boron,-   tripropylammoniumtetra(o,p-dimethylphenyl)boron,-   tributylammoniumtetra(m,m-dimethylphenyl)boron,-   tributylammoniumtetra(p-tri-fluoromethylphenyl)boron,-   tributylammoniumtetra(pentafluorophenyl)boron,-   tri(n-butyl)ammoniumtetra(o-tolyl)boron, and the like;    N,N-dialkylanilinium salts such as:-   N,N-dimethylaniliniumtetraphenylboron,-   N,N-diethylaniliniumtetraphenylboron,-   N,N-2,4,6-pentamethylaniliniumtetraphenylboron and the like;    dialkyl ammonium salts such as:-   diisopropylammoniumtetrapentafluorophenylboron,-   dicyclohexylammoniumtetraphenylboron and the like;    triaryl phosphonium salts such as:-   triphenylphosphoniumtetraphenylboron,-   trimethyl phenylphosphoniumtetraphenylboron,-   tridimethylphenylphosphoniumtetraphenylboron and the like, and their    aluminum equivalents.

In yet another embodiment, an alkylaluminum may be used in conjunctionwith a heterocyclic compound. The ring of the heterocyclic compound mayinclude at least one nitrogen, oxygen, and/or sulfur atom, and includesat least one nitrogen atom in one embodiment. The heterocyclic compoundincludes 4 or more ring members in one embodiment, and 5 or more ringmembers in another embodiment.

The heterocyclic compound for use as an activator with an alkylaluminummay be unsubstituted or substituted with one or a combination ofsubstituent groups. Examples of suitable substituents include halogen,alkyl, alkenyl or alkynyl radicals, cycloalkyl radicals, aryl radicals,aryl substituted alkyl radicals, acyl radicals, aroyl radicals, alkoxyradicals, aryloxy radicals, alkylthio radicals, dialkylamino radicals,alkoxycarbonyl radicals, aryloxycarbonyl radicals, carbomoyl radicals,alkyl- or dialkyl-carbamoyl radicals, acyloxy radicals, acylaminoradicals, aroylamino radicals, straight, branched or cyclic, alkyleneradicals, or any combination thereof. The substituents groups may alsobe substituted with halogens, particularly fluorine or bromine, orheteroatoms or the like.

Non-limiting examples of hydrocarbon substituents include methyl, ethyl,propyl, butyl, pentyl, hexyl, cyclopentyl, cyclohexyl, benzyl or phenylgroups and the like, including all their isomers, for example tertiarybutyl, isopropyl, and the like. Other examples of substituents includefluoromethyl, fluoroethyl, difluoroethyl, iodopropyl, bromohexyl orchlorobenzyl.

In one embodiment, the heterocyclic compound is unsubstituted. Inanother embodiment one or more positions on the heterocyclic compoundare substituted with a halogen atom or a halogen atom containing group,for example a halogenated aryl group. In one embodiment the halogen isselected from the group consisting of chlorine, bromine and fluorine,and selected from the group consisting of fluorine and bromine inanother embodiment, and the halogen is fluorine in yet anotherembodiment.

Non-limiting examples of heterocyclic compounds utilized in theactivator of the invention include substituted and unsubstitutedpyrroles, imidazoles, pyrazoles, pyrrolines, pyrrolidines, purines,carbazoles, and indoles, phenyl indoles, 2,5,-dimethylpyrroles,3-pentafluorophenylpyrrole, 4,5,6,7-tetrafluoroindole or3,4-difluoropyrroles.

In one embodiment, the heterocyclic compound described above is combinedwith an alkyl aluminum or an alumoxane to yield an activator compoundwhich, upon reaction with a catalyst component, for example ametallocene, produces an active polymerization catalyst. Non-limitingexamples of alkylaluminums include trimethylaluminum, triethylaluminum,triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum,tri-iso-octylaluminum, triphenylaluminum, and combinations thereof.

Other activators include those described in WO 98/07515 such astris(2,2′,2″-nonafluorobiphenyl) fluoroaluminate, which is incorporatedby reference herein. Combinations of activators are also contemplated bythe invention, for example, alumoxanes and ionizing activators incombinations. Other activators include aluminum/boron complexes,perchlorates, periodates and iodates including their hydrates; lithium(2,2′-bisphenyl-ditrimethylsilicate)-4T-HF; silylium salts incombination with a non-coordinating compatible anion. Also, methods ofactivation such as using radiation, electro-chemical oxidation, and thelike are also contemplated as activating methods for the purposes ofrendering the neutral metallocene-type catalyst compound or precursor toa metallocene-type cation capable of polymerizing olefins. Otheractivators or methods for activating a metallocene-type catalystcompound are described in for example, U.S. Pat. Nos. 5,849,852,5,859,653 and 5,869,723 and WO 98/32775.

In general, the activator and catalyst component(s) are combined in moleratios of activator to catalyst component from 1000:1 to 0.1:1 in oneembodiment, and from 300:1 to 1:1 in a more particular embodiment, andfrom 150:1 to 1:1 in yet a more particular embodiment, and from 50:1 to1:1 in yet a more particular embodiment, and from 10:1 to 0.5:1 in yet amore particular embodiment, and from 3:1 to 0.3:1 in yet a moreparticular embodiment, wherein a desirable range may include anycombination of any upper mole ratio limit with any lower mole ratiolimit described herein. When the activator is a cyclic or oligomericpoly(hydrocarbylaluminum oxide) (e.g., “MAO”), the mole ratio ofactivator to catalyst component ranges from 2:1 to 100,000:1 in oneembodiment, and from 10:1 to 10,000:1 in another embodiment, and from50:1 to 2,000:1 in a more particular embodiment. When the activator is aneutral or ionic ionizing activator such as a boron alkyl and the ionicsalt of a boron alkyl, the mole ratio of activator to catalyst componentranges from 0.5:1 to 10:1 in one embodiment, and from 1:1 to 5:1 in yeta more particular embodiment.

More particularly, the molar ratio of Al/metallocene-metal (Al from MAO)ranges from 40 to 500 in one embodiment, ranges from 50 to 400 inanother embodiment, ranges from 60 to 300 in yet another embodiment,ranges from 70 to 200 in yet another embodiment, ranges from 80 to 175in yet another embodiment; and ranges from 90 to 125 in yet anotherembodiment, wherein a desirable molar ratio of AI(MAO) tometallocene-metal “M” may be any combination of any upper limit with anylower limit described herein.

The activators may or may not be associated with or bound to a support,either in association with the catalyst component (e.g., metallocene) orseparate from the catalyst component, such as described by Gregory G.Hlatky, Heterogeneous Single-Site Catalysts for Olefin Polymerization100(4) CHEMICAL REVIEWS 1347-1374 (2000).

Metallocene Catalysts may be supported or unsupported. Typical supportmaterials may include talc, inorganic oxides, clays and clay minerals,ion-exchanged layered compounds, diatomaceous earth compounds, zeolitesor a resinous support material, such as a polyolefin.

Specific inorganic oxides include silica, alumina, magnesia, titania andzirconia, for example. The inorganic oxides used as support materialsmay have an average particle size of from 30 microns to 600 microns, orfrom 30 microns to 100 microns, a surface area of from 50 m²/g to 1,000m²/g, or from 100 m²/g to 400 m²/g, a pore volume of from 0.5 cc/g to3.5 cc/g, or from 0.5 cc/g to 2 cc/g.

Desirable methods for supporting metallocene ionic catalysts aredescribed in U.S. Pat. Nos. 5,643,847; 0,918,4358 and 09184389, whichare incorporated by reference herein. The methods generally includereacting neutral anion precursors that are sufficiently strong Lewisacids with the hydroxyl reactive functionalities present on the silicasurface such that the Lewis acid becomes covalently bound.

When the activator for the metallocene supported catalyst composition isa NCA, desirably the NCA is first added to the support compositionfollowed by the addition of the metallocene catalyst. When the activatoris MAO, desirably the MAO and metallocene catalyst are dissolvedtogether in solution. The support is then contacted with theMAO/metallocene catalyst solution. Other methods and order of additionwill be apparent to those skilled in the art

Those skilled in the art will appreciate that modifications in the abovegeneralized preparation method may be made without altering the outcome.Therefore, it will be understood that additional description of methodsand means of preparing the catalyst are outside of the scope of theinvention, and that it is only the identification of the preparedcatalysts, as defined herein, that is necessarily described herein.

The copolymers may be prepared via conventional polymerization processessuch as are well known in the art. Examples of such polymerizationprocesses include slurry, liquid-bulk and gas-phase polymerizations. Inslurry polymerization processes, polymerization occurs in the presenceof a solvent, e.g. hexane, within a loop or continuous stirred tankreactor. Polymerization may also be carried out by bulk-phasepolymerization, where liquid propylene and ethylene serve as bothmonomer and diluent. In a typical bulk process, one or more loopreactors are generally employed. In other embodiments the copolymer maybe produced by gas phase polymerization of propylene and ethylene, whichis typically carried out in a fluidized bed reactor. Polymer fluff orpowder produced from the polymerization reaction is removed from thereactor and may then be processed via conventional techniques, such asby extrusion, to produce the desired copolymer pellets.

The amount of ethylene monomer used during polymerization of thecopolymer is desirably in proportion to the desired final ethylenecontent of the target propylene-ethylene copolymer. In some embodimentsthe ethylene content may range from about 0.01 to about 10 percent byweight of the copolymer as a whole, more desirably from about 0.1 toabout 8 percent by weight, and most desirably from 0.5 to 5 percent byweight. In other embodiments effective levels of ethylene may range from0.5 to 2 percent, and in still others from 1 to 2 percent, based on,total weight of the copolymer.

The selected metallocene catalyst may provide a propylene-ethylenerandom copolymer having lower xylene solubles content, as compared tothose copolymers of the same ethylene content prepared from conventionalZiegler-Natta catalysts. “Xylene solubles content” is defined as thatproportion of the copolymer as a whole that is soluble in xylene. Sincecharacterization as isotactic generally indicates insolubility of thepolymer in xylene, it is believed that certain chain defects within apredominantly isotactic chain, and/or very low molecular weight chains,are the cause of a minor portion of the polymer being xylene-soluble.Thus, a reduced xylene solubles content implies increased isotacticityand therefore increased crystallinity, which in turn indicates improvedclarity.

In particular, the xylene solubles content for the random copolymers,having an ethylene content desirably from about 0.5 to about 3 percentby total weight of copolymer, more desirably from about 0.5 to about 2percent by total weight of copolymer, may total less than about 2percent. In various embodiments a xylene solubles content of about 1.5or less by weight of copolymer may be attained. In embodiments where theethylene content is greater than about 3 percent by weight of copolymer,for example, from about 3 to about 5 percent by weight, a xylenesolubles content of from about 2 to about 3 percent may be attained.

The propylene-ethylene copolymers may be characterized as having amolecular weight distribution, defined as weight average molecularweight divided by number average molecular weight (Mw/Mn), that may benarrower than that of similar copolymers prepared using conventionalcatalysts. Desirably the molecular weight distribution of the resins maybe less than about 5, more particularly from about 2 to about 4. Therelatively narrower molecular weight distribution may in someembodiments contribute to the reduced xylene solubles content and,therefore, also to the improvements in clarity attainable herein.

Because of their desirable properties, the copolymers may beparticularly suitable for injection molding applications. Theseproperties may include a melt flow rate (MF) of from about 0.1 g/10 minto about 150 g/10 min, with from about 10 to about 60 g/10 min beingtypical, and from about 15 to about 30 g/10 min being more typical, asdetermined by ASTM D-1238, Procedure B. Unless otherwise indicated, allmelt flow rates presented herein are measured according to ASTM D-1238,Procedure B.

Significantly, the copolymers may exhibit improved clarity (alsoreferred to as reduction in haze) without unacceptable loss inmechanical properties such as tensile strength, flexural modulus andnotched Izod impact strength. In particular, as much as a 40 percentreduction in haze may be achieved without significant detriment to suchproperties, as compared to the haze performance of copolymers of thesame or similar melt flow rate and ethylene content that have beenprepared by other methods such as via conventional Ziegler-Nattacatalysis. Such improvement may render the copolymers particularlydesirable for use in preparing injection molded or extruded films,sheets and other products which similarly include relativelyclosely-spaced parallel surfaces such as walls. These products mayinclude, for example, injection molded bottles and other containers.

In preparing injection molded articles, the copolymer may be introduced,along with any selected additives, into an injection molding unit. Hereit may be simultaneously mixed, heated and pressurized until the desiredfinal melt temperature, viscosity and pressure are obtained. Typically,the final melt temperature prior to injection is from about 340 to about600° F. (171-315° C.), with pressures ranging from about 100 to about30,000 psi (0.7-207 mPa). The pressurized molten polymer is theninjected through an injection nozzle into a mold having a mold cavity ofthe desired shape. Once the molten copolymer has cooled and solidifiedwithin the mold, the mold is opened to release the molded article. Theprocess may then be repeated. Where walls are included in the structure,their thicknesses in many typical applications may desirably range fromabout 0.01 (0.254 mm), desirably 0.02 (0.501 mm), to about 0.25 inch(6.35 mm), but may in some embodiments be thicker.

While the copolymers may exhibit improved clarity, even without use ofconventional clarity-enhancing agents, it is still possible to includesuch clarity-enhancing agents for even greater clarity improvement. Whenused they are preferably in an amount of from about 0.01 to about 0.75percent by total weight of resin. As used herein, the expression“clarity-enhancing agent” may include those categorized as eitherclarifying agents and/or as nucleating agents. Suitable clarifyingagents include the acetals of sorbitols and xylitols as well asphosphate ester salts. Many such clarifying agents are disclosed in U.S.Pat. No. 5,310,950, which is incorporated herein by reference. Specificexamples of acetals of sorbitols include (p-methylbenzylidene) sorbitoland 2,4 bis(3,4-dimethyldibenzylidene) sorbitol. Examples of suitablecommercially available sorbitol-acetal clarifying agents are thosedesignated as Millad 3940 and Millad 3988, both available from MillikenChemical, Spartanburg, S.C. Specific examples of phosphate ester saltsinclude 2,2-methylene-bis(4,6-ditertbutylphenyll)phosphate, and aluminumhydroxybis(2,4,8,10-tetrakis(1,1-dimethyl)6-hydroxy-12H-dibenzo[d,g][1,2,3][dioxaphophocin 6-oxidato]. Examples ofcommercially available phosphate ester salts for use as clarifyingagents include ADK stabilizer NA-11A and ADK Stabilizer NA-21, bothavailable from Amfine Chemical Corp., Allendale, N.J. Combinations ofany of the above may also be employed.

If a clarifying agent will be used for a given application, it isdesirably in an amount of at least about 0.01 percent by weight ofcopolymer. More desirably the clarifying agent is used in an amount offrom 0.05 to about 0.75, still more desirably from about 0.10 to about0.5, and most desirably from about 0.15 to about 0.3, percent by weightof copolymer. The clarifying agent, along with other additives, may beadded to the copolymer during extrusion or prior to injecting molding.

In some embodiments a clarity-enhancing agent selected from the categoryknown as nucleating agents may also or optionally be employed. Whilefrequently used, these additives are often somewhat less effective thanthe clarifying agents. Suitable nucleating agents may include mineralssuch as talc, aromatic carboxylic salts, dicarboxylic acid salts, andcombinations of these and/or of the clarifying agents. Sorbitol acetalsand phosphate ester salts, discussed hereinabove, may also act aseffective nucleating agents. Specific examples of aromatic carboxylicsalts may include sodium benzoate and lithium benzoate, whiledicarboxylic acid salts may includecis-endo-bicyclo-heptane-2,3-dicarboxylic acid disodium salt.

Nucleating agents may desirably be employed in amounts of from about0.01 to 0.75 percent by weight of the copolymer, with from about 0.05 toabout 0.50 percent by weight being more typical. More typically thenucleating agent is used in an amount of from 0.01 to about 0.75 percentby weight, still more typically from about 0.05 to about 0.5 percent byweight, and most typically from about 0.10 to about 0.5 percent byweight of copolymer. Where combinations of nucleating agents andclarifying agents are used, similar weight percentages, as combined, aredesirable.

The attainable clarity performance of the copolymers will thus dependupon whether or not one or more clarity-enhancing agents are employedand the performance and proportion of such agents, as well as theethylene content of the copolymer, its xylene solubles content, its meltflow rate, and the thickness of the article in which it is being used.For example, in some embodiments injection molded articles formed fromcopolymers which have an ethylene content of from about 0.5 to about 3percent by weight, and which have been modified with clarity-enhancingagents, may exhibit a haze value of less than about 20 percent at athickness of about 0.08 inch (2.03 mm). Further improvements may be seenfor embodiments where the copolymer has a similar ethylene content, buta lower melt flow rate. In these cases the melt flow rate is desirablyless than about 20 g/10 min or less, more desirably about less thanabout 15 g/10 min, and still more desirably from about 7 g/10 min toabout 15 g/10 min. In such embodiments an injection molded articleexhibiting less than about 13 percent haze at a thickness of about 0.08inch (2.03 mm) may be obtained.

Desirable performance for the copolymers may also be seen in embodimentswhere the copolymer has a relatively higher ethylene content, inparticular, greater than about 3 percent by weight, desirably from about3 to about 5 percent by total weight of the copolymer, and a xylenesolubles content of less than about 4 percent by weight. In such casesthe invention may provide an injection molded article exhibiting lessthan about 13 percent haze at a thickness of about 0.08 inch (2.03 mm).Copolymers of similar ethylene content, but with a lower melt flow rate,in particular, a melt flow rate of less than about 20 g/10 min, and moredesirably from about 7 g/10 min to about 15 g/10 min, may provide aninjection molded article exhibiting less than about 10 percent haze at athickness of about 0.08 inch (2.03 mm).

With respect to other physical properties, additional improvements maybe attained. For example, in some embodiments an copolymer that has amelt flow rate of greater than about 20 g/10 min may also exhibit aflexural modulus of less than about 2.25×10⁵ psi, (1551 mPa) asdetermined by ASTM D790-97. In other embodiments, those having a meltflow rate of greater than 20 g/10 min may exhibit a flexural modulus ofless than 1.5×10⁵ psi (1034 mPa), as determined by ASTM D790-97.

Examples of articles and products that may be prepared using thepropylene-ethylene random copolymers include injection molded products,such as housewares, food storage containers, cooking utensils, plates,cups, measuring cups, drinking cups, strainers, turkey basters, non-foodstorage containers, filing cabinets and particularly clear drawers usedin such cabinets, and general storage devices, such as organizers,totes, sweater boxes, and the like. Other articles and products includerigid packaging, such as deli containers and lids including those usedfor dips, spreads, and pasta salads, dairy containers and lids includingthose used for storing cottage cheese, butter and yogurt, personal careproducts, and bottles and jars. In these and other uses the resins maybe combined with other materials, such as particulate materials,including talc, calcium carbonate, wood, and fibers, such as glass orgraphite fibers, to form composite materials. Examples of such compositematerials include components for furniture, automotive components andbuilding materials, particularly those used as lumber replacement.

The propylene-ethylene copolymers may also be used for other articles,such as films, coatings and fibers. In other embodiments the resins arealso suitable for blow molding and thermoforming. Examples of sucharticles are bags, adhesives, yarns and fabrics, bottles and jars, andplates and cups.

The following examples serve to merely illustrate the invention andshould not be construed as limiting its scope in any way. While theinvention has been shown in only some of its forms, it should beapparent to those skilled in the art that it is not so limited, but issusceptible to various changes and modifications without departing fromthe scope of the invention. For example, modifications of ethylenecontent, xylene solubles content, haze performance, processing means andmethods, catalyst selections, additives selections, and the like, notexplicitly disclosed herein but falling within the generalizeddescription, may be made without departing from the scope hereof.Accordingly, it is appropriate that the appended claims be construedbroadly and in a manner consistent herewith.

EXAMPLES

Unless otherwise specified, all properties set forth in the followingexamples use the following testing methods. Tensile strength is measuredaccording to ASTM D638-97. Flexural modulus is measured according toASTM D790-97. Izod and Gardner impact strength are measured according toASTM D256-97 and ASTM D1709, respectively. DSC recrystallization andmelt peaks are measured according to ASTM D3417-97 and ASTM D418-97,respectively. Finally, haze values are measured according to ASTM D1003on plaques formed using step chip molds of varying thickness having anSPI A-1 chrome finish.

Example 1 and Comparative Example 1

Clarified metallocene-catalyzed propylene-ethylene random copolymers(cmRCP) are compared with clarified Ziegler-Natta-catalyzedpropylene-ethylene random copolymers (cZNRCP) of similar melt flow rateof less than 20 g/10 min and with varying ethylene content. Both theexample and comparative copolymers are prepared using a conventionalslurry polymerization reactor under substantially identical conditionsof temperature, pressure, feed rate, reactant selection and proportion,and residence time. However, the polymerization to form the exampleemploys as a catalyst that is a racemic solution ofMe₂Si(2-Me-4-Phlnd)₂ZrC₁₂ and Me₂Si(2-Me-Phlnd)₂ZrCl₂, activated by0.7/1 methylaluminoxane (MAO), supported on P10 silica, which is achiral, stereo-rigid metallocene catalyst. In contrast, the catalystsused for the comparative resins are both conventional Ziegler-Nattacatalysts. Resins designated with “EOD” are commercially available fromTotal USA; other designations are as supplied by their manufacturers. Ineach case a clarifying agent identified as MilIad™ 3988, which isdescribed by its manufacturer, Milliken Chemical, as an organicderivative of dibenzylidene sorbitol, is included in the formulation inthe amounts shown in Table 1.

The additives are compounded with each copolymer via co-extrusion usinga 1% inch WELEX™ extruder using a temperature profile of from 375 to475° F. from the rear of the extruder to the die. Following extrusionthe copolymers are each injection molded into tensile strength andNotched Izod test bars using ASTM methods D-638 and D-256, respectively.Step chip molds for haze measurements are also prepared using extrudertemperature profiles which range, from the rear of the extruder to thedie, from 400 to 450° F. (204-232° C.), with a mold temperature of115-117° F. (46-47° C.) and a back pressure of 100 psi (0.7 mPa). Theresults are presented in Table 1 below.

TABLE 1 Sample No. 1 (Ex.) 2 (Ex.) 3 (Ex.) 4 (Ex.) 5 (Comp.) 6 (Comp.)EOD-0014 EOD-0029 EOD-0029 EOD-0026 7525 MZ 8573 cmRCP cmRCP cmRCP cmRCPcZNRCP cZNRCP MFI, g/10 min 15 15 15 13 10 10 Xylene Solubles 0.5-1 2-32-3 2-3 2-5 4.5-8 Content, wt. % Ethylene, wt. % 1 2 3 5 2 4 Millad ™3988, 0.25 0.25 0.25 0.25 0.2 0.2 wt. % Haze, % at given thickness: 20mil 3 2 2 2 4 5.5 40 mil 6 5 4 4 8 13 60 mil 9 9 7 7 11 22 80 mil 12 109 8 15 28 Tensile Strength 4800 (33) 4400 (30) 4000 (28) 2700 (19) 4200(29) — at break, psi (mPa) 2% Flexural    2.1 (1448)    1.8 (1241)   1.4(965)   0.7 (482)    1.7 (1172) — Modulus, 1 × 10⁵ psi (mPa) NotchedIzod, 0.5 1.2 1.9 5.5 1.3 3.9 ft.lb./in. — Dashed line indicates no dataavailable.

Example 2 and Comparative Example 2

Clarified metallocene-catalyzed propylene-ethylene random copolymers(cmRCP) are compared with clarified Ziegler-Natta-catalyzedpropylene-ethylene random copolymers (cZNRCP) of similar melt flow rateof at least about 20 g/10 min and with varying ethylene content. Thecopolymers used for Samples 7 and 8, available from Total USA, areprepared as in Example 1, except using different metallocene catalysts.Additives, including clarifying agent, are the same as in Example 1 andComparative Example 1, and compounding, extrusion, test bar formation,and all aspects of testing are carried out using the same procedures asin Example 1 and Comparative Example 1. The results are presented inTable 2 below.

TABLE 2 8 (Ex.) 10 7 (Ex.) EOD- (Comp.) EOD-0031 0031 7823-MZ SamplecmRCP cmRCP cZNRCP MFI, g/10 min 30 32 29 Xylene Solubles 0.5-1 0.5-14.5-6 Content, wt. % Ethylene, wt. % 1 2 3 Millad ™ 3988, wt. % 0.210.22 0.19 Haze, % at given thickness: 20 mil 4 3 4 40 mil 9 7 9 60 mil13 11 16 80 mil 18 15 20 Tensile Strength, psi 4600 4200 3400 (mPa)(32)  (29)  23) Flexural Modulus, psi 2.0 1.7 3.4 (1 × 10⁵) (mPa) (1379)(1172) (2344) Notched Izod, ft.lb./in. 0.4 0.7 1.1

It may be seen in the example that, as compared to Ziegler-Nattacatalyzed polymer, the metallocene-catalyzed copolymer may be usedeffectively to prepare injection molded articles, in particular, havingreduced haze at comparable stiffness. It follows, then, that when acomparable haze level is desirable or acceptable, the article mayexhibit a desirably higher stiffness.

furniture components, building materials and building containercomponents, films, coatings, fibers, bags, adhesives, yarn and fabric.

1-24. (canceled)
 25. A process comprising: supplying an isotacticpropylene-ethylene random copolymer resin having an ethylene content offrom about 0.5 to about 3 percent by total weight of the isotacticpropylene-ethylene random copolymer, a melt flow rate of from about 0.1g/10 min to about 150 g/10 min as determined by ASTM D-1238, ProcedureB, and a xylene solubles content of less than about 2 percent by totalweight of the isotactic propylene-ethylene random copolymer; andinjection molding the isotactic propylene-ethylene random copolymerresin to form an injection molded article, wherein the injection moldedarticle exhibits a haze of less than about 20 percent, as determined byASTM 01003, at a thickness of about 0.08 inch (2.03 mm).
 26. The processof claim 25, wherein the isotactic propylene-ethylene random copolymerresin has a melt flow rate of less than about 20 g/10 min, as determinedby ASTM D-1238, Procedure B, and the injection molded article exhibits ahaze of less than 13 percent, as determined by ASTM 01003, at athickness of about 0.08 inch (2.03 mm).
 27. The process of claim 26,wherein the isotactic propylene-ethylene random copolymer resin has amelt flow rate of from about 7 g/10 min to about 15 g/10 min.
 28. Theprocess of claim 25, wherein the isotactic propylene-ethylene randomcopolymer resin has a melt flow rate of greater than about 20 g/10 min,as determined by ASTM D-1238, Procedure B.
 29. The process of claim 28,wherein the injection molded article exhibits a flexural modulus of lessthan about 2.25×10⁵ psi (1551 mPa), as determined by ASTM 0790-97. 30.The process of claim 25, wherein the isotactic propylene-ethylene randomcopolymer resin comprises a clarity-enhancing agent in an amount of fromabout 0.01 to about 0.5 percent by total weight of isotacticpropylene-ethylene random copolymer resin.
 31. The process of claim 30,wherein the clarity-enhancing agent is selected from the groupconsisting of acetals of sorbitols, acetals of xylitols, phosphate estersalts, minerals, aromatic carboxylic salts, dicarboxylic acid salts, andcombinations thereof.
 32. The process of claim 25, wherein the isotacticpropylene-ethylene random copolymer resin has an ethylene content offrom about 0.5 to about 2 percent by total weight of isotacticpropylene-ethylene random copolymer.
 33. The process of claim 25,wherein the injection molded article is selected from a group consistingof housewares, food storage containers, cooking utensils, plates, cups,drinking cups, measuring cups, strainers, turkey basters, non-foodstorage containers, filing cabinets, cabinet drawers, general storagedevices, organizers, totes, sweater boxes, rigid packaging, delicontainers, deli container lids, dairy containers, dairy container lids,personal care products, bottles and jars, furniture, furniturecomponents, building materials and building container components, films,coatings, fibers, bags, adhesives, yarn and fabric.
 34. The process ofclaim 25, wherein the resin comprises a clarity-enhancing agent in anamount of at least 0.01 percent by total weight of resin; wherein theisotactic propylene-ethylene random copolymer resin is catalyzed in thepresence of a catalyst selected from metallocene catalysts and has amelt flow rate of greater than about 20 g/10 min as determined by ASTMD-1238, Procedure B; and wherein the injection-molded article exhibits aflexural modulus of less than about 2.25×10⁵ psi, as determined by ASTMD790-97.
 35. The process of claim 34, wherein the injection-moldedarticle exhibits a flexural modulus of less than about 1.5×10⁵ psi, asdetermined by ASTM D790-97 and a haze of less than about 13 percent, asdetermined by ASTM D1003, at a thickness of about 0.08 inch (2.03 mm);and wherein the isotactic propylene-ethylene random copolymer resin hasan ethylene content of from about 1 to about 2 percent by total weightof copolymer; a melt flow rate of from greater than about 20 g/10 min upto 60 g/10 min, as determined by ASTM D-1238, Procedure B, a xylenesolubles content of less than about 1.5 percent by total weight ofcopolymer; and a molecular weight distribution of from 2 to
 4. 36. Aprocess comprising: supplying an isotactic propylene-ethylene randomcopolymer resin having an ethylene content of greater than about 3percent by total weight of the copolymer, a melt flow rate of from about0.1 g/10 min to about 150 g/10 min as determined by ASTM D-1238,Procedure B, and a xylene solubles content of less than about 4 percentby total weight of the copolymer; and injection molding the isotacticpropylene-ethylene random copolymer resin to form an injection moldedarticle, wherein the injection molded article exhibits a haze of lessthan about 13 percent, as determined by ASTM 01003, at a thickness ofabout 0.08 inch (2.03 mm).
 37. The process of claim 36, wherein theisotactic propylene-ethylene random copolymer resin has an ethylenecontent of from about 3 to about 5 percent by total weight of thecopolymer.
 38. The process of claim 36, wherein the isotacticpropylene-ethylene random copolymer resin has a xylene solubles contentof from about 2 to about 3 percent by total weight of the copolymer. 39.The process of claim 36, wherein the isotactic propylene-ethylene randomcopolymer resin has a melt flow rate of less than about 20 as determinedby ASTM D-1238, Procedure B, and wherein the injection molded articleexhibits a haze of less than about 10 percent, as determined by ASTM01003, at a thickness of about 0.08 inch (2.03 mm).
 40. The process ofclaim 39, wherein the isotactic propylene-ethylene random copolymerresin has a melt flow rate of from about 7 to about 15 as determined byASTM D-1238, Procedure B.
 41. The process of claim 36, wherein theisotactic propylene-ethylene random copolymer resin has a melt flow rateof greater than about 20 g/10 min, as determined by ASTM D-1238,Procedure B.
 42. The process of claim 41, wherein the injection moldedarticle exhibits a flexural modulus of less than about 2.25×10⁵ psi(1551 mPa), as determined by ASTM 0790-97.